US6038083AExpiredUtility
Compact zoom lens
Est. expiryMar 26, 2017(expired)· nominal 20-yr term from priority
Inventors:Kenichi Sato
G02B 15/143103
36
PatentIndex Score
5
Cited by
8
References
19
Claims
Abstract
A compact zoom lens including three lens groups having positive, positive and negative refractive power, in order from the object side. The distance between the first and second lens groups, as well as the distance between the second and third lens groups, is decreased when zooming from the maximum wide angle state to the maximum telephoto state. Aberrations are made favorable, even when in the maximum wide-angle state, by satisfying prescribed conditional expressions as well as by specifying prescribed lens element shapes for the first lens group and the third lens group. By arranging a negative meniscus lens element at the front of the first lens group with its concave surface on the photographic object side, curvature of field and distortion, which otherwise become a problem when in the maximum wide-angle, are suppressed. By arranging, immediately behind the negative meniscus lens element, a positive meniscus lens with its convex surface on the photographic object side, the back-focus of the compact zoom lens can be held short. Furthermore, in the third lens group, by arranging a negative meniscus lens element at the extreme photographic object side, and by figuring each surface of this lens element to be aspheric, the usual deterioration in imaging performance which accompanies compactness can be effectively prevented. Further, a diaphragm stop 2 is arranged between the first lens group G1 and the second lens group G2.
Claims
exact text as granted — not AI-modifiedWhat is claimed is:
1. A compact zoom lens which comprises, in order from a photographic object side: a first lens group of positive refractive power, said first lens group including the surface nearest the photographic object side of said compact zoom lens; a second lens group of positive refractive power; a diaphragm stop located between said first lens group and said second lens group; and, a third lens group of negative refractive power; wherein the distance between said second lens group and said third lens group is reduced when zooming from a maximum wide-angle state to a maximum telephoto state, the distance between said first lens group and said second lens group is reduced when zooming from the maximum wide-angle state to the maximum telephoto state, and said first lens group includes a negative meniscus lens element having its concave surface on the object side.
2. The compact zoom lens as set forth in claim 1, said first lens group further including a positive meniscus lens element.
3. The compact zoom lens as set forth in claim 2, said positive meniscus lens element having its convex surface on the photographic object side.
4. The compact zoom lens as set forth in claim 1, wherein said second lens group comprises at least one lens element having a surface that is convex.
5. The compact zoom lens as set forth in claim 4, said first lens group further including a negative meniscus lens element having its concave surface on the photographic object side.
6. The compact zoom lens as set forth in claim 5, said first lens group further including a positive meniscus lens element with its convex surface on the photographic object side.
7. The compact zoom lens as set forth in claim 6, wherein said third lens group comprises, in order from the photographic object side, a meniscus lens element having an aspheric surface, a positive lens element having a convex surface on the image side, and a negative meniscus lens element with its concave surface on the photographic object side.
8. The compact zoom lens as set forth in claim 7, and wherein the following conditional expressions are satisfied: 0.6<f'.sub.g12 /f'.sub.w <1.4 (1) f'.sub.g1 /f'.sub.g2 <15 (2) D.sub.12 <1.5 (3) where f' g12 is the composite focal length in the maximum wide-angle state of the first lens group and second lens group, f' w is the focal length of the compact zoom lens when in the maximum wide-angle state, f' g1 is the focal length of the first lens group, f' g2 is the focal length of the second lens group, and D 12 is the ratio of the distance between the first lens group and the second lens group when at the maximum wide-angle state divided by the distance between the first lens group and the second lens group when at the maximum telephoto state.
9. The compact zoom lens as set forth in claim 1, wherein said third lens group comprises, in order from the photographic object side, a meniscus lens element having an aspheric surface, a positive lens element having a convex surface on the image side, and a negative meniscus lens element with its concave surface on the photographic object side.
10. The compact zoom lens as set forth in claim 9, and wherein the following conditional expressions are satisfied: 0.6<f'.sub.g12 /f'.sub.w <1.4 (1) f'.sub.g1 /f'.sub.g2 <15 (2) D.sub.12 <1.5 (3) where, f' g12 is the composite focal length in the maximum wide-angle state of the first lens group and second lens group, f' w is the focal length of the compact zoom lens when in the maximum wide-angle state, f' g1 is the focal length of the first lens group, f' g2 is the focal length of the second lens group, and D 12 is the ratio of the distance between the first lens group and the second lens group when at the maximum wide-angle state divided by the distance between the first lens group and the second lens group when at the maximum telephoto state.
11. The compact zoom lens as set forth in claim 1, and further comprising the compact zoom lens having the construction parameters as set below: ______________________________________
# R D N.sub.d ν.sub.d
______________________________________
1 -13.311 1.47 1.84665 23.9
2 -18.369 0.10
3 21.037 2.37 1.51824 59.0
4 100.544 variable (3.43-2.75)
5 -45.950 1.79 1.48749 70.4
6 -26.574 0.10
7 -29.204 2.59 1.49577 81.6
8 -15.882 variable(7.38-0.07)
9 -14.627 1.45 1.49023 57.5
10 -22.485 0.10
11 -193.684 1.60 1.80518 25.5
12 -42.751 3.80
13 -8.379 1.07 1.66704 44.0
14 -66.348
______________________________________
where R is the radius of curvature in mm of each lens element surface #, in order from the object side, D is the on-axis surface spacing in mm, N d is the index of refraction, and ν d the Abbe number of each lens element, and wherein the surfaces 3, 4, 8, 9 and 10 are figured so as to be aspheric.
12. The compact zoom lens as set forth in claim 1, and further comprising the compact zoom lens having the construction parameters as set forth below: ______________________________________
# R D N.sub.d
v.sub.d
______________________________________
1 -11.765 1.47 1.84665
23.9
2 -17.013 0.10
3 27.470 2.37 1.60222
41.3
4 87.421 variable (4.67-3.44)
5 29.520 1.79 1.74186
87.1
6 77.793 0.10
7 25.480 2.59 1.49577
81.6
8 -16.354 variable (7.19-0.88)
9 -14.468 1.45 1.49700
57.5
10 -22.120 0.10
11 -265.009 1.60 1.80518
25.5
12 -41.395 3.34
13 -8.833 1.07 1.81500
44.4
14 -59.695
______________________________________
where # is the surface number from the object side, R is the radius of curvature in mm of each lens element surface, D is the on-axis surface spacing in mm, N d is the index of refraction and ν d the Abbe number for the sodium d line of each lens element, and wherein the surfaces 3, 4, 8, 9, 10, and 13 are figured so as to be aspheric.
13. The compact zoom lens as set forth in claim 1, and further comprising the compact zoom lens having the construction parameters as set forth below: ______________________________________
# R D N.sub.d
v.sub.d
______________________________________
1 -11.889 1.47 1.84665
23.9
2 -16.468 0.10
3 22.635 2.37 1.49251
58.7
4 116.515 variable (3.87-3.14)
5 -65.271 1.79 1.50226
69.5
6 -28.153 0.10
7 23.980 2.59 1.49577
81.6
8 -16.027 variable (7.02-1.02)
9 -14.658 1.45 1.49023
57.5
10 -22.323 0.10
11 -250.180 1.60 1.80518
25.5
12 -42.460 3.34
13 -8.533 1.07 1.81550
44.4
14 -55.926
______________________________________
where # is the surface number in order from the object side, R is the radius of curvature in mm of each lens element surface, D is the on-axis surface spacing in mm, N d is the index of refraction and ν d is the Abbe number for the sodium d line of each lens element, and wherein the surfaces 3, 4, 8, 9, and 10 are figured so as to be aspheric.
14. A compact zoom lens which comprises, in order from a photographic object side: a first lens group of positive refractive power, said first lens group including the surface of said compact zoom lens nearest the photographic object side of said compact zoom lens; a second lens group of positive refractive power; a diaphragm stop located between said first lens group and said second lens group; and, a third lens group of negative refractive power; wherein, the distance between said second lens group and said third lens group is reduced when zooming from a maximum wide-angle state to a maximum telephoto state; and said first lens group includes a negative meniscus lens element which has its concave surface on the photographic object side.
15. The compact zoom lens as set forth in claim 14, said first lens group fisher including a positive meniscus lens element.
16. The compact zoom lens as set forth in claim 15, said positive meniscus lens element having its convex surface on the photographic object side.
17. The compact zoom lens as set forth in claim 14, wherein said second lens group comprises at least one lens element having a surface that is convex.
18. The compact zoom lens as set forth in claim 17, said first lens group further including a positive meniscus lens element with its convex surface on the photographic object side.
19. The compact zoom lens as set forth in claim 17, wherein said third lens group comprises, in order from the photographic object side, a meniscus lens element having an aspheric surface, a positive lens element having a convex surface on the image side, and a negative meniscus lens element with its concave surface on the photographic object side.Join the waitlist — get patent alerts
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